Vectorized link cell Fortran code for molecular dynamics simulations for a large number of particles

A highly efficient procedure for calculating forces in a molecular dynamics simulation on a vector computer is described. The algorithm is feasible for several thousand particles on currently available machines. The efficiency comes about by a combination of a Verlet table with a link cell algorithm. By a double list data structure, that treats the pairs of interacting particles in a symmetrical manner, the vectorization can be improved significantly. Moreover, the "layering algorithm" recently described by Rapaport can be incorporated. A standard Fortran formulation of the basic procedure is given. We test the algorithm on a Cray XMP/416 for two different Lennard-Jones fluids with interactions truncated at 2 1 6 α and 2.5 α. The CPU time is shown to increase linearly with system size. Our link cell method proves to be more efficient than a straightforward search over all pairs as soon as the particle number exceeds about 500. © 1989.